The Mentored Research Scientist Development Award In Molecular Epidemiology is requested to support the career development of Dr. Susan Teitelbaum, who is a classically trained cancer epidemiologist. The primary aim of the K01 grant is to position Dr. Teitelbaum as an independent research scientist specializing in the environmental and molecular epidemiology of combined effects of multiple exposures. The research aims, relating multiple xenoestrogen exposure to breast cancer risk, will be examined in the Long Island Breast Cancer Study Project, a large population-based case-control study of breast cancer and the environment. Traditional chronic disease epidemiology focuses on single risk factor-disease associations at the individual level with little consideration of the combined effect of multiple exposures, particularly those of similar biological action. Dr. Teitelbaum's career goal is to advance beyond the investigation of single exposure-disease relationships by incorporating advanced data analytic approaches not yet commonly used in epidemiology. Her training program will enable her to acquire in-depth knowledge of advanced statistical methods for examining the combined effect of multiple exposures and gene-environment interactions, a better understanding of the laboratory methods used to assess biomarkers of xenoestrogen exposure, and experience in working with genetic polymorphisms. The training program includes obtaining a Master's degree in biostatistics, laboratory rotations, and attendance at carefully chosen symposia and national meetings. Dr. Teitelbaum's proposal is sponsored by Dr. Mary Wolff (environmental/molecular epidemiology), Dr. Gertrud Berkowitz (epidemiology), and Dr. Sylvan Wallenstein (biostatistics). Additional advisors will be Drs. James Wetmur (environmental genetics) and Avrom Caplan (nuclear receptors). Breast cancer is an estrogen-related disease and xenoestrogens are strongly suspected to be environmental risk factors for breast cancer. With the exception of organochlorine compounds (including DDT, DDE and PCBs), little research has been directed at these environmental chemicals and even less has been focused on the combined effect of these hormonally active agents. Results of the proposed research project will be of enormous public health relevance since they may advance our knowledge of modifiable breast cancer risk factors, thereby providing information that is essential for primary prevention. Furthermore, data analysis approaches applied in this research project will be applicable to a wide range of environmentally associated diseases.